1. Field of the Invention
The present invention relates to a valve seat used with a diaphragm valve in a so-called treater tank and to a method of repairing eroded valve seats used in such valves.
2. Description of the Background
Treaters, or vertical treater tanks, are used in the oil and gas industry to separate the components of an emulsion pumped from an oil well. Typically, such an emulsion contains salt water, oil and natural gas. The salt water from a group of wells is collected in a central location tank and then pumped back to the downhole formation. The oil, separated from the water and gas, is collected in storage tanks which are periodically emptied into tank trucks for transfer to a refinery. The gas which is separated is directed to a suitable pipeline for transfer to market.
The vertical treaters or treater tanks employed are described, for example, in a publication entitled "Vertical Treater Start-Up Operational and Maintenance Guide," C-E Netco, Combustion Engineering, Inc., December 1962. The vertical treaters employ check valves to effect and control flow of the oil and water to their respective collection tanks. The operation and construction of such valves is well known to those skilled in the art and described, for example, in a publication entitled "Treater Oil and Water Valves," Kimray, Inc., September 1986.
Basically, the valves in the treater have a valve seat formed of a generally tubular, metallic body with a cylindrical bore therethrough. The valve seat is threadedly received in the lower part of the valve body, the other end of the valve seat forming a sealing surface which is engaged by a seal element carried by a diaphragm assembly which, when engaged with the sealing surface on the valve seat, closes the valve and when retracted from the sealing surface opens the valve. The body of the valve seat adjacent the annular sealing surface is prone to erosion because of cavitation. When this occurs, a fluid-tight seal is lost with the consequence that valuable amounts of gas which is used as the driving force are lost, the gas escaping to the water or oil collection locations. Accordingly, it becomes necessary to shut down the operation of the treater, remove the valve seat and replace it with a new valve seat. Thus, the erosion of the valve seats is expensive, since it results in substantial losses of marketable gas and because the new valve seats are costly to replace.